Home' News Bulletin : ADA News Bulletin April 2016 Contents PRACTICE
EALs are now widely accepted by practitioners, especially because they
can reduce the general number of radiographs required for working
length determination.3 Current EALs have high reliability, accuracy
and reproducibility in locating the apical foramen regardless of the
electrolyte inside the canal.4 For devices using the methodology of the
RootZX [J Morita Corp, Kyoto, Japan] the overall accuracy was reported
to range from 82%5 to 100%.6 Modern devices have numeric metre
readings which show the distance of the file tip to the apex during
measurements in the apical region. For most devices, these numbers
should be handled with great care. The measurement is typically precise
directly at or very close to the foramen.7 It is advisable to approach this
point with the file and then measure the length of the file.
EALs are typically precise if the electrical circuit can be closed (no
obliterated canals), if a significant foramen is still existing (no cases
with severe apical opening) and if no other currents are interfering
with the measurement (like conductive crowns, vertical fractures or
Apart from detecting the recommended endpoint with increased
accuracy, one of the biggest advantages is that measurements can
be obtained quickly, repeatedly and without problems like pain or
EALs are comparably cheap devices. Lip- and instrument-clips need to
be sterilised, have a limited lifetime and need to be replaced regularly.
EALs use very low voltage and currents and are generally safe for
patients and dentists. However, there is a controversial discussion in
literature regarding the possibility of electromagnetic interference
(EMI) to cardiovascular implantable devices (CVID) like pacemakers
and cardioverter defibrillators. Although many studies conclude
that the use of EALs is generally safe in patients with CVIDs,8-10
recent studies have found, that EMI is possible under certain
In conclusion, the clinical advantage of EALS and the possible threat
to patients with CVIDs should be weighted carefully, especially
because the radiological method is a safe alternative.
RECOMMENDATIONS FOR CLINICAL USE
A cost-benefit analysis of EALs reveals they are very useful devices
for endodontic treatment. Every practitioner with an interest in
endodontic treatment should consider buying one.
Use EALs in an early stage of treatment
As the measurement process works very well even with small file
sizes (ISO #10) it is advised to start in the very early phase of the
endodontic treatment to have length information available before
any damage can be done to the foramen.
Fig 2: Modern style EAL [Root ZX mini, J Morita Corp, Kyoto, Japan]. The
green bar shows the adjustable mark for the apical constriction.
Professor Richard Stoll
James Cook University
On behalf of the Dental Instruments, Materials and
Check if unsure
In some situations, the measurement process of the EAL may be
impeded, this can be recognised by noticing no measurement at all,
or by a jumping metre reading as the file approaches or passes the
foramen. Normally, this should be a smooth movement displayed
on the metre scale. In these situations, it is highly advisable to
take a conventional radiograph with a file or silver point set at the
Adjust and check
If you use a new EAL, it is advisable to use it together with a
radiological method for a number of cases to compare the results.
Some EALs can be adjusted for an individual reading of AC (Fig 2).
The radiographic method of length determination produces its own
evidence of clinical care. EALs do not create pictures, so the results
should be meticulously documented in the patient file and also the
clinical consequences and decisions.
Computer aided measurement strategies used in the latest
generation of EALs have not increased overall precision which
remains dominated by the Morita Root ZX type devices. Methods of
combining EALs with endodontic handpieces for rotary files provide
continuous length control during work. The integration of this
information into the motor control electronics, e.g. to stop or alter
the file motion if the apical endpoint is reached is an example of
utilising length information in an integrated tool.
References are available on request from email@example.com
"FAILURE TO DETERMINE THE CORRECT
WORKING LENGTH...HAS THE POTENTIAL
TO SIGNIFICANTLY INCREASE THE FAILURE
PROBABILITY OF ROOT CANAL TREATMENT."
ADA NEWS BULLETIN | APRIL 2016 | 37
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